Numerous diseases of Man and animals are carried by sucking arthropods as a primary vector of infection. Causative agents of these diseases include viruses, bacteria and rickettsia, each of which is transferred to Man and animals by the arthropod's bite.
Diseases which may be transmitted to Man or animals by the tick include Lyme Disease (also known as Borreliosis, Lyme Borreliosis-associated Encephalopathy, Lyme Arthritis, acrodermatitis chronica atrophicans, erythremia chronicurn migrans, Banwarth's syndrome, tick-borne meningopolyneuritis, Lyme meningitis, collectively hereinafter termed "Lyme Disease"). The causative organism of Lyme Disease is the spirochete Borrelia Burgdorferi. Other tick-borne diseases include Rocky Mountain Spotted Fever (causative agent, Rickettsia rickettsii); Q fever (causative agent, Rickettsia burnetii); Tularemia (causative agent, Pasteurella tularensis); South African Tick Bite Fever (causative agent, Rickettsia pijperi); Mediterranean fever (causative agent, Rickettsia conori); Human Babeosis (causative agent, Babesia Microti); epidemic Typhus (causative agent, Rickettsia prowazekii); and Scrub Typhus (causative agent, Rickettsia tsutsugamushi). Even anaphylaxis has been caused by the attachment and bite of an arthropod (Ixodus pacificus). See, e.g. Boyd, A TEXTBOOK OF PATHOLOGY, Eighth Edition, Asian Edition, Lee and Febiger (1976), pp. 395-399 and pp. 71 6; Robbins, PATHOLOGY, third edition, W.B. Saunders, Philadelphia (1967), pp. 349-353.
The most ubiquitous of such sucking arthropods is commonly referred to as the tick, of which there are numerous species and subspecies. Ticks established to be disease vectors include Ixodes dammini (commonly termed the deer tick), Ixodes scapularis, Amblyomma arnericanum, Amblyomma maculatum, Ixodes pacificus, Ixodes ricinus, Ixodes persulcatus, Ixodes hyocyclus, Dermacentor andersoni. See Sigal and Curran, Ann. Rev. Publ. Health 12: 85-109 (1991); also Tetlow et al. Am. J. Trop. Medo Hygiene 44:469-474 (1991); See also Piesman et al., J. Clin. Microbiol. 25: 2012-2013 (1987).
("Disease Organism" refers to any of the viral, bacterial or rickettsial microbiological agents which are normally contained in the gut or vascular system of the infected tick, and which may be transmitted to Man or Animals during the sustained attachment of the tick to the dermis or subcutaneous tissues of such mammalian species. "Tick" refers to any of the species of arthropods which are named above as significant vectors for the infectious organisms in the disease of Man and Animals enumerated above.)
Lyme Disease is probably the most widespread and frequently encountered arthropod-borne disease. It is particularly problematic to treat because it is an essentially multisystem inflammatory disease with complex symptomatology often not unique to the disease. Consequently, considerable confusion has taken place in attempts to diagnose Lyme Disease due to the absence, until recently, of reliable immunological tests for the organism. Diagnosis has been even more challenging in those cases where an initial skin lesion does not appear in a reasonable time following the tick bite. Additionally, even when Lyme Disease is correctly diagnosed, there have been problems in treating it: despite antibiotic therapy, Lyme Disease sometimes presents chronic symptoms.
Therefore, efforts have been made to prevent Lyme Disease, and other tick-borne diseases, by eradicating tick populations from areas where Man and animal are likely to become infected. However, it is exceedingly difficult to rid an area of Lyme Disease-carrying vectors. One reason is that carrier ticks, generally of the family Ixodes, are usually present as a very highly concentrated population. Many animals in a given area themselves carry ticks harboring the Lyme Disease causative agent; non-domesticated animals infected with B. Burgdorferi generally include coyotes, deer, mice, jackrabbits, raccoons and hamsters, while domesticated animals which may be infected include cats, dogs, cows, horses, and sheep. Chemical means for clearing areas heavily infected with carrier ticks have failed to demonstrate significant reproducible lowering of Lyme Disease prevalence. Application of such agents not only has dubious effectiveness in reducing Lyme Disease morbidity; these agents may themselves have toxic impact on other wildlife and so render their use undesirable.
Lyme Disease is also preventable by removal of the sucking arthropod soon after its bite. This has generally not been an effective prophylactic measure to date because tick bites are often undetectable or ignored. Nevertheless, if tick removal occurs soon enough after the bite, the arthropod will not have had time to transfer disease organisms to the Man or animal host.
The importance of prompt tick removal is made clear by the correlation between the time a tick remains attached after biting its host and the number of infections caused by tick-borne organisms in a controlled population. This correlation is demonstrated by the data in TABLE 1, showing the time-course for which the tick must remain attached in order for demonstrated spirochetal infection to occur in the rabbit (adapted from the data of Piesman et al., supra).
TABLE 1 ______________________________________ Hours Number of Infection of Attachment Ticks/Rabbit Observed ______________________________________ 24 15 NO 36 19 NO 48 15 NO &gt;120 16 YES ______________________________________
It is important to note that prophylaxis by removal of the tick depends upon the entire arthropod being removed from host flesh. If removal is not complete, then head, mouth or feeding parts may remain in the host flesh. These parts may and often do contain disease organisms and hence are still capable of transmitting disease-causing organisms for up to several days after removal of most of the tick. To be effective as a means of disease prophylaxis, removal of the entire tick is crucial. Complete removal also constitutes a diagnostic aid. Thus when the complete, untraumatized tick body is successfully removed from host flesh, the tick may readily be classified taxonomically or immuno-histochemically. Thus, one may determine whether the tick is one which may bear disease organisms.
It is exactly this completeness of removal which poses a major difficulty in prophylaxis of Lyme Disease and other arthropod-borne diseases. Due to its small size (0.3-2 mm in length), once the tick has bitten a host and the host's tissue surrounding the bite has swollen, the head and abdomen of the tick usually become wholly or partially surrounded or submerged in the host's epidermis. Therefore, only a small area of the tick may be gripped with a forceps or other removal tool. Further, the head and particularly the mouth parts also have an exceedingly retentive hold in the host skin. Thus, the parts most difficult to disengage cannot readily be grasped. Finally, when the exposed part of the tick is grasped during removal, the very tight hold by the mouth parts frequently causes breakage of the tick body, even when experienced medical personnel attempt removal of an arthropod.
Unfortunately, this important aspect of disease prophylaxis has received comparatively little attention, and incorrect methods of tick removal are abundant in both the professional literature and popular literature. Old wives' tales suggesting that kerosene, petroleum jelly, or a lit match or cigarette are effective in tick removal are simply unreliable. These methods should be eschewed, as they may actually cause the tick to regurgitate into the wound and cause infection. It is actually desirable for ticks to be removed with thin tweezers or forceps using antiseptic precautions.
Prior art compositions have employed refrigerant (U.S. Pat. No. 4,834,967) and gas anesthetic compounds (U.S. Pat. No. 4,534,128 and 4,624,070) for tick removal or control, respectively. U.S. Pat. No. 4,834,967 discloses ticks removal from the skin of a mammal by means of a liquid refrigerant applied to the skin to freeze, kill, and dislodge the tick. The liquid refrigerants disclosed include Freon R-12, Freon R-22, Freon R-502, liquid nitrogen, and liquid carbon dioxide. The refrigerant is said to kill the tick by freezing it. Although application of such refrigerants could cause temporary numbness to the dermis of the mammal to which it was applied, the refrigerant does not act as a local anesthetic. Furthermore, the tick is said to be killed by freezing; it appears no selective paralysis of the tick occurs.
U.S. Pat. Nos. 4,534,128 and 4,624,070 disclose use of a general anesthetic, dimethyl ether, for pest control. A method of immobilizing and killing insects in their dwelling place by applying mixtures of dimethyl ether and various insecticides (not repellents) in a directed spray, and an apparatus for said application, are described. While dimethyl ether gas is a general anesthetic, it is not used as an anesthetic due to its relatively toxic effect in animals and Man.
Given the difficulty of removing sucking arthropods from host skin coupled with the desirability of doing so to prevent Lyme Disease, there has been a long-felt need for compositions facilitating the simple, effective and a traumatic removal of attached sucking arthropods from human or animal skin. Such compositions should be safe for handling by laymen. These compositions should also effect complete removal of the tick; this would further allow subsequent characterization of the tick by taxonomical and/or immunological means. The compositions should also act rapidly to facilitate tick removal, prevent infection and reduce inflammation of tissue at or surrounding the bite, and enhance quick removal of ticks.
There has been an equally long felt need for methods which facilitate removal of attached sucking arthropods from human or animal skin.
(Citation of documents herein is not intended as an admission that any of the documents cited herein is pertinent prior art, or an admission that the cited documents is considered material to the patentability of the claims of the present application. All statements as to the date or representation as to the contents of these documents is based upon the information available to the applicant and does not constitute any admission as to the correctness of the dates or contents of these documents.)